Field of the Invention
The present invention relates to techniques for diagnosing faults in a vehicle charging system for charging a battery mounted on the vehicle.
Description of the Related Art
In conventional electrically driven vehicles such as electric vehicles and plug-in hybrid vehicles in which a charger mounted on a vehicle is connected to an external power supply via a charging gun to charge a battery mounted on a vehicle, a starting circuit is mounted which detects connection of a charging gun to the vehicle and causes the charger to output a charging start signal to a control unit of the vehicle to activate the control unit so that the battery can be charged even while the power supply of the vehicle is turned off (ignition switch is off).
A variety of fault diagnostic devices have hitherto been proposed for such vehicles configured to be recharged by means of an external power supply. In Japanese Patent No. 4586888 by way of example, the frequency of diagnosis of various faults in vehicle-mounted devices is changed depending on whether an external power supply is connected or not, thereby securing an adequate frequency of diagnosis while at the same time restraining the consumption of electric power of the battery mounted on a vehicle.
In the aforementioned type of vehicles whose control unit can be activated when charging is to be started, a charging start signal circuit is provided which connects the charger and the control unit to allow a charging start signal to be output from the charger to the control unit.
However, if disconnection, power-supply short circuit or grounding fault occurs in the charging start signal circuit, the charging start signal may possibly fail to be input to the control unit accurately, making charging itself unachievable. Thus, there has been a demand for diagnosing faults in the charging start signal circuit.